GtkWidget::path

string path();

Obtains the full path to the widget. The path is simply the name
of a widget and all its parents in the container hierarchy, separated
by periods. The name of a widget comes from
get_name() .
Paths are used to apply styles to a widget in gtkrc
configuration files.
Widget names are the type of the widget by default (e.g. "GtkButton")
or can be set to an application-specific value with
set_name() . By setting the name
of a widget, you allow users or theme authors to apply styles to that
specific widget in their gtkrc file.